System and Method for Rapidly Stopping a Spinning Table Saw Blade

ABSTRACT

A system for stopping a spinning table saw blade is comprised of a pin assembly disposed adjacent to a saw blade assembly for stopping a spinning saw blade. A receiving block is disposed on a side of the saw blade opposing the pin assembly for receiving the tip of the pin assembly. A driving assembly is coupled to the pin assembly for driving the pin assembly into the spinning saw blade into the receiving block. Finally, a sensing assembly is coupled to at least one of the saw blade assembly and the driving assembly for sensing encroachment of a user&#39;s hand in a pre-defined zone. In use, upon sensing a user&#39;s hand the sensing assembly signals the driving assembly to stop the spinning saw blade by driving the pin assembly through the saw blade and into the receiving block.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 10/836,132 filed Apr. 29, 2004 (Attorney Docket No.DEL 03-8-2), which in-turn claims priority under 35 USC §119(e) toprovisional U.S. Application No. 60/466,199 filed Apr. 29, 2003(Attorney Docket No. DEL 03-8-1). In addition, the present applicationclaims priority entitled under 35 U.S.C. §119(e) to provisional U.S.Application No. 60/533,192 filed Dec. 30, 2003 (Attorney Docket No. DEL03-47-1). Said U.S. patent application Ser. No. 10/836,132 and U.S.Provisional Patent Applications Nos. 60/466,199 and 60/533,192 areherein incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to the field of saws and moreparticularly to a detection system and method for rapidly stopping aspinning saw blade.

BACKGROUND OF THE INVENTION

There exists a need for an effective method to rapidly stop a spinningsaw blade in response to input from a sensing device that detectspossible contact of the blade with a user's hand. Currently, variousmethods of stopping a saw blade under such conditions are available. Forexample, some methods employ a brake which makes contact with the bladeand causes the blade to drop below the table surface if the user's handhas made contact with the saw blade. Additional methods utilize athree-in-one system including a splitter, anti-kickback fingers and ablade cover.

All of the presently available systems and methods have one or moredisadvantages in terms of convenience of use, early and effectivedetection of a user's hand and cost. For instance, the system whichemploys a brake mechanism destroys the saw blade when used. Further,such system requires contact be made between the user and the bladeprior to activation of the braking mechanism. Additionally, employmentof the three-in-one system severely limits the flexibility of themachine (e.g. user is limited to making through-cuts because thesplitter sits higher than the blade, any partial cut such as a groove ora joint may not be done without removing the entire system).

Therefore, it would be desirable to design a system and a method forstopping a rapidly spinning table saw blade overcoming theaforementioned limitations of inflexibility and required user/saw bladecontact thereby resulting in an efficient, flexible, early to detectstopping system.

SUMMARY OF THE INVENTION

In a first aspect of the invention, a system for stopping a spinning sawblade is disclosed. Such system is comprised of a pin assembly disposedadjacent to a saw blade assembly for stopping a spinning saw blade. Areceiving block is disposed on a side of the saw blade assembly opposingthe pin assembly for receiving the tip of the pin assembly. A drivingassembly is coupled to the pin assembly for driving the pin assemblyinto the spinning saw blade into the receiving block. Finally, a sensingassembly is coupled to at least one of the saw blade assembly and thedriving assembly for sensing encroachment of a user's hand in apre-defined zone. In use, upon sensing a user's hand the sensingassembly signals the driving assembly to stop the spinning saw blade bydriving the pin assembly through the saw blade and into the receivingblock. In additional embodiments of the present invention, the sensingassembly includes shape recognition technology. Further, the pinassembly is actuated by an explosive substance wherein the explosivesubstance is contained within a replaceable cartridge.

In a second aspect of the invention, a method for stopping a rapidlyspinning saw blade is disclosed. Such method is comprised of detecting auser's hand in a pre-defined zone by a detecting system and driving apin assembly through the saw blade into a receiving block to stop thesaw blade from spinning upon detecting the presence of a user's hand.

BRIEF DESCRIPTION OF DRAWINGS

The numerous advantages of the present invention may be betterunderstood by those skilled in the art by reference to the accompanyingfigures in which:

FIG. 1 is an isometric view of a table saw including a sensing assemblyin accordance with an exemplary embodiment of the present invention,wherein the sensing assembly includes a video proximity device fordetecting a user's hand in a pre-defined zone;

FIG. 2 is an isometric illustration in accordance with the videoproximity device provided in FIG. 1, wherein the video proximity devicefurther includes a laser;

FIG. 3 is an exploded, isometric view of the table saw shown in FIG. 2,illustrating the indication by a laser beam, visible on the hand of theoperator, that encroachment into a predefined zone has occurred;

FIG. 4 is a front view of a table saw in accordance with an exemplaryembodiment of the present invention, wherein the components of thedetection system located beneath the table top of the table saw areillustrated;

FIG. 5 is an exploded partial view of the table saw illustrated in FIG.4, wherein the pin assembly is retracted;

FIG. 6 is an exploded partial view of the table saw illustrated in FIG.4, wherein the pin assembly has been actuated; and

FIG. 7 is flow chart illustrating a method for stopping a rapidlyspinning table saw in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the presently preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

Referring in general to FIGS. 1-6, a detection system for rapidlystopping a spinning saw blade in response to input from a sensing devicethat detects possible contact of the blade with a user's hand isdisclosed. In use, upon sensing a user's hand in a pre-defined zone, asensing assembly signals a driving assembly to stop the rapidly spinningsaw blade by driving a pin assembly through the saw blade and into areceiving block. In one embodiment, the detection system becomesactivated prior to a user's hand making contact with the saw blade whichis a major advantage over the prior art which requires such contact.Further, the detection system is positioned to allow an workspace on thetable top surface to be unobstructed. In additional embodiments, the pinassembly is actuated by an explosive or detonation substance which maybe easily replaced after use. As such, the instant invention overcomesthe limitations of partial blade disintegration, inflexibility andrequired user/saw blade contact and thus, yields an efficient, flexible,early to detect stopping system.

Referring in general to FIGS. 1-3, an exemplary embodiment of a sensingassembly included within the instant detection system is disclosed. Thesensing assembly is for sensing encroachment of a user's hand in apre-defined zone. In the present embodiment, the sensing assembly iscoupled to the saw blade and the driving assembly (not shown, see FIGS.4-6). Further, in the exemplary embodiment, the sensing assembly iscomprised of a video proximity device. The video proximity device maydetect the presence of a human body part, such as a human hand and thelike, in a predefined zone or point about the working tool element of apower tool. Moreover, in an exemplary embodiment of the presentinvention, the video proximity device is configured to distinguishbetween a workpiece, like wood, within the predefined zone or point, anda human body part. The presence of a body part in the predefined zone orpoint is detected through the use of a video camera positioned for aclear view of the working tool element and the adjacent area. Should abody part enter this zone or point, the sensing assembly initiatesappropriate countermeasures to prevent contact. For example, the sensingassembly directs the driving assembly to drive the pin assembly into thesaw blade to stop the spinning of such blade. In addition to or in thealternative of stopping the saw blade, the sensing assembly causes powerto the saw assembly to be shut-off or for the blade to be mechanicallymoved away from the user, and the like for preventing contact betweenthe user and working tool.

The video proximity device may utilize a number of different techniquesfor detecting the presence of a human body part. In one embodiment, thevideo from the video proximity device is analyzed by an informationhandling system (e.g. a computer) having pattern recognition hardware orsoftware for identifying the unique shapes and patterns of human bodyparts, as differentiated from the shapes and patterns of a workpiece.For example, a human hand is comprised of a series of rounded edges,while a workpiece generally includes linear edges. In anotherembodiment, an information handling system includes motion analysishardware or software capable of detecting the movement of a human bodypart, as differentiated from the movement of a workpiece. For example, ahuman hand moves in a non-linear, or somewhat erratic, manner, while aworkpiece is directed in a line parallel to the orientation of a toolelement. In a further embodiment, the video camera comprises a thermalimaging camera, capable of distinguishing the heat signature of a humanbody part from the heat signature of a workpiece. For example, a humanbody part is typically of a higher temperature than the temperature of aworkpiece in the same environment, and thus is distinguishable by such asystem. It should be noted that one of skill in the art may contemplateother video processing and recognition techniques without departing fromthe scope and intent of the present invention.

The video proximity device may be positioned in a number of differentorientations in order to provide a substantially unobstructed view ofthe working tool element and the adjacent area. In one embodiment, thevideo proximity device is mounted on an assembly above the supportsurface. For example, in the case of a table saw, a video camera ismounted on a support assembly above the saw blade, providing a view ofthe blade and surrounding area. In another embodiment, the videoproximity device is mounted to the power tool itself. For example, inthe case of a table saw, a video camera is mounted in the fence of thetable saw, providing a generally unobstructed view of the blade andsurrounding area. Additionally, fiber optic cameras may be desirable inorder to minimize intrusion and the like.

The video proximity device may be employed in concert with varioussystems for alerting the operator of their encroachment into apredefined zone or point. In one embodiment, the support surface of thepower tool is clearly marked to indicate the limits of one or morepredefined zones. For example, in the case of a table saw, a “red zone”is clearly marked on the support surface, indicating that if anoperator's body part encroaches into this zone, the saw blade will bestopped by driving a pin assembly into the side of the saw blade. Itshould be noted that more than one zone may be defined, and the videoproximity device may be capable of distinguishing encroachment intodifferent zones. This may serve not only to provide an additional signalto the operator, but also to minimize the situations in which the pinassembly is actuated. In the case of the table saw, the red zone issurrounded by a caution zone or “yellow zone,” for example. If anoperator's hand encroaches into the caution/yellow zone, power to themotor driving the saw blade or the working tool is terminated, or thetool is moved below a support surface, causing no permanent damage tothe saw blade. Such a configuration may have the added benefit ofproviding a gradual slowdown for the working tool element. In the caseof a table saw utilizing a yellow zone/red zone combination, forexample, initially slowing the saw blade in the yellow zone allows theblade to be stopped more quickly and more effectively in the red zone,reducing potential harm to an operator and to the power tool.

In another embodiment of the sensing assembly, a laser device is usedwith the video proximity device for clearly marking the boundaries of azone. In one embodiment, the laser device projects a beam of visiblelight onto the support surface/workpiece, indicating to an operator thelimits of the zone. This configuration provides the added benefit ofvisually indicating to the operator encroachment into the zone outlinedby the beam, which may appear on the encroaching part of the operator'sbody.

Referring specifically to FIG. 1, a video proximity device is shown fora table saw assembly 100 in accordance with an exemplary embodiment ofthe first aspect of the present invention. The table saw assembly 100includes a saw blade 102 surrounded by a red zone 104 and a cautionzone/yellow zone 106. A video camera 110 is located directly above thetable saw assembly 100, mounted on a support assembly 112. The supportassembly 112 provides passage for cables 114 associated with the videocamera 112. These cables supply power to the video camera 110 andconnect the output of the video camera 110 to a computer or processorhaving hardware or software for discerning the presence of a human bodypart in the zones. Upon encroachment of a body part into the yellow zone106, action is taken by the table saw assembly 100 to stop the saw blade102. This action may include eliminating power to a motor driving thesaw blade 102. Upon encroachment of a body part into the red zone 104,action is taken by the table saw assembly 100 directed toward stoppingthe saw blade 102 in a more definite manner. For example, a pin assembly126 is directed into the saw blade 102 or the saw blade 102 is removedto below the support surface of the table saw assembly 100.

Referring specifically to FIG. 2, a video proximity device is shown fora table saw assembly 100 in accordance with an exemplary embodiment ofthe present invention. The table saw assembly 100 includes a saw blade102 surrounded by a red zone 104 and a yellow zone 106. A video camera110 is located directly above the table saw assembly 100, mounted on asupport assembly 112. The support assembly 112 provides passage forcables 114 associated with the video camera 112. These cables supplypower to the video camera 110 and connect the output of the video camera110 to a information handling system having hardware or software fordiscerning the presence of a human body part in the red zone 104 and theyellow zone 106. A laser device 120 is included with the video camera110 and projects a laser beam 122 onto the workpiece/support surface ofthe table saw assembly 100. Upon encroachment of a body part into theyellow zone 106, an operator is visually cued by the reflectance of thelaser beam 122 from a body part encroaching into the zone, and actionmay be taken by the table saw assembly 100 to stop the saw blade 102.For example, such action includes terminating power to a motor poweringthe saw blade 102. Further, upon encroachment of a body part into thered zone 104, action is taken by the table saw assembly 100 directedtoward stopping the saw blade 102 in a more definite manner. Forexample, the pin assembly 126 is directed into the saw blade 102 or thesaw blade 102 is dropped below the support surface of the table sawassembly 100.

Referring specifically to FIG. 3, a laser beam 122 is shown contacting abody part 124 encroaching into a red zone 104 in accordance with a firstaspect of the present invention. The laser beam 122 may serve as avisual cue to the operator that encroachment into the red zone 104 hasoccurred. It should be noted that the area enclosed by the laser beam122 may correspond with the red zone 104, the yellow zone 106 (See FIGS.1 and 2), or any number of predefined zones or points. It should also benoted that an operator of a power tool utilizing a video proximitydevice may define the area of a zone dynamically, and the laser beam 122may be used to indicate the boundaries of such a zone. It should her benoted that a number of laser beam generating devices may be used toindicate a number of different zones, as contemplated by one of skill inthe art.

In the alternative to the sensing assembly including a video proximitydevice, such assembly may recognize the difference in the electricalproperties of wood and a user whereby the system projects ahigh-frequency electrical signal on the saw blade and monitors changesin the signal such as by utilizing one of the assemblies presently knownin the art. For example, under normal operating conditions, the signalwould remain unaltered for wood includes a relatively small inherentelectrical capacitance and conductivity and therefore, the presence ofwood in the electrical field would not result in an alteration of suchfield. However, if a user's hand made contact with the saw blade 102,the detection system 100 would be activated by the sensing assemblydetecting a change in the electrical signal as a result of therelatively large inherent capacitance of the user's body. For instance,contact detection electrodes are coupled to the saw blade to detectfluctuations in capacitance.

As illustrated in FIGS. 4-6, the stopping system disclosed in theinstant invention includes a pin assembly 126. The pin assembly 126 isdisposed on a first side of the saw blade 102 for stopping a spinningsaw blade. Further, the pin assembly 126 includes a first end. In oneembodiment, the first end includes a pointed tip for piercing the sawblade. In additional embodiments, the pin assembly 126 is comprised ofheat-treated steel thereby increasing the strength and durability of thepin assembly 126. It is contemplated that additional materials includingsteel or other metals may be utilized without departing from the scopeand spirit of the present invention. Moreover, the size and shape of thepin assembly 126 may vary depending upon the size and dimensions of thesaw blade 102 which is to be pierced; however, preferably, suchvariation will be limited to that which will not result in thesignificant disintegration of the saw blade 102.

In addition to the pin assembly 126, the stopping system includes adriving assembly 128. In an exemplary embodiment, the driving assembly128 is coupled to the pin assembly 126 for driving the pin assembly 126into the spinning saw blade 102. Further, the driving assembly 128includes a communication system which allows the driving assembly 128 tocommunicate with the sensing assembly. For example, the driving assembly128 may be hard-wired 130 to the sensing assembly as demonstrated inFIG. 4. In additional embodiments, the driving assembly 128 may beactivated by the sensing assembly via an optical signal from the sensingassembly.

Moreover, in an exemplary embodiment of the present invention, anexplosive or capable of detonation substance is coupled to a pistonwhich upon actuation causes the pin assembly 126 to be propelled intothe spinning saw blade. The explosive actuated pin assembly 126 resultsin such assembly making an instantaneous forced entry into the saw blade102 causing the saw blade 102 to stop spinning immediately. As such, inone embodiment, the explosive substance is contained in a replaceablecartridge 132 (e.g. a blank cartridge including a .22 or a .27 caliberload). In additional embodiments, the drive assembly 128 may beelectromagnetic, mechanical (e.g. a spring system or mallet activated),or the like. It will be appreciated that activation of the pin assembly126 by the drive assembly 128 will generally require the replacement ofthe explosive substance (e.g. the replaceable cartridge, 132). However,use of a replaceable cartridge system will allow a user to easilyreplace the explosive substance prior to resuming use of the saw.

In a further embodiment of the present invention, a receiving block 134is disposed on the second side of the saw blade 102 for receiving thetip of the pin assembly 126. In one exemplary embodiment, as illustratedin FIGS. 5 and 6, the receiving block 134 includes an aperture 136 forreceiving the tip of the pin assembly 126. Use of the aperture 136allows the pin assembly 126 to be received by the receiving block 134while minimizing the damage to the pin assembly 126 due to interactionwith the receiving block 134. Further, the receiving block 134 may beformed of any suitable metal including steel, heat-treated steel, or thelike so that contact by the pin assembly 126 does not destroy thereceiving block 134.

FIGS. 5 and 6 illustrate the pin assembly in either a retracted positionor an actuated position, respectively. In FIG. 5, the pin assembly 126is in the retracted position and the replaceable cartridge 132 is readyfor use. In an exemplary embodiment, upon sensing a user's hand or otherbody part in a predefined zone, the sensing assembly (see FIGS. 1-3)directs the driving assembly 128 to drive the pin assembly 126 into therapidly spinning saw blade 102. The driving assembly 128 actuates thepin assembly 126 by firing the explosive substance contained in thereplaceable cartridge 132 causing the instantaneous firing of the pinassembly 126 through the saw blade 102 into the receiving block 134. Asillustrated in FIG. 6 and as discussed previously, the receiving block134 may be configured with an aperture 136 for receiving the pinassembly 126. In an exemplary embodiment, the size and shape of theaperture 136 corresponds to that of the pin assembly 126.

In an additional embodiment, the pin assembly 126 may be retracted fromthe saw blade 102 and the receiving block 134 by blowing compressed airthrough a port hole 138 located within the drive assembly 128. Such porthole 138 also functions as an exit for the air generated during therelease of the explosive substance.

In still a further embodiment, the detection system 100 may include aself-check feature whereby each time the table saw is turned on, thedetection system 100 performs a system check to ensure that the systemis properly working. If the system is not properly working, the user maybe notified by a warning signal including flashing lights or power beingcut to the motor. In an additional embodiment, the detection system 100may include a bypass feature which would allow the system to be turnedoff if necessary. For example, if the sensing assembly is triggered bydetecting a difference in capacity, if a user desires to cut a piece ofmetal with such saw it would be preferable to turn-off the detectionsystem. The detection system may be set-off unnecessarily whereby thecapacitance of a piece of wood is much less than that of a piece ofmetal and thus, the system may sense a change in capacitance due to thetype of material being cut not because of entry of a users hand into apredefined zone. Those of skill in the art will appreciate that whilethe present drawings illustrate the present invention in use on a tablesaw, such invention may be adapted to be coupled to variety of powertools including a miter saw, chop saws, radial arm saws, circular saw,and the like without departing from the scope and spirit of the presentinvention.

In addition to the detection system, a method for stopping a spinningsaw blade 200 is disclosed. As illustrated in FIG. 7, such method iscomprised of cutting material with a saw blade 202. Upon detecting auser's hand in a pre-defined work zone by a detecting system 204, thedetecting system including a sensing device, a drive assembly, a pinassembly and a receiving block transmits directions from the sensingdevice to the drive assembly to drive the pin assembly into the sawblade 206. The drive assembly then drives the pin assembly 124 throughthe saw blade 104 into the receiving block 130 to stop the saw blade 104from spinning 208. It is contemplated that the instant method 200 may beutilized with a number of different power tools including a miter saw,circular saw, chop saws, radial arm saws, table saw, and the like.

It is believed that the present invention and many of its attendantadvantages will be understood by the foregoing description, and it willbe apparent that various changes may be made without departing from thescope and spirit of the invention or without sacrificing all of itsmaterial advantages. The form herein before described being merely anexplanatory embodiment thereof, it is the intention of the followingclaims to encompass and include such changes.

Further, it is understood that the specific order or hierarchy of stepsin the methods disclosed are examples of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the method can be rearranged while remainingwithin the scope of the present invention. The accompanying methodclaims present elements of the various steps in a sample order, and arenot meant to be limited to the specific order or hierarchy presented.

1. A system for stopping a spinning saw blade, comprising: a pinassembly disposed adjacent to a saw blade assembly for stopping thespinning saw blade, the pin assembly including a first end, the firstend including a pointed tip for piercing the saw blade; a receivingblock disposed on a side of the saw blade opposing the pin assembly forreceiving the tip of the pin assembly; a driving assembly coupled to thepin assembly for driving the pin assembly into the spinning saw bladeand into the receiving block; and a sensing assembly coupled to at leastone of the saw blade assembly and the driving assembly for sensingencroachment of a user's hand in a pre-defined zone, wherein uponsensing a user's hand the sensing assembly signals the driving assemblyto stop the spinning saw blade by driving the pin assembly through thesaw blade and into the receiving block.
 2. The detection system of claim1, wherein the sensing system comprises a video proximity device.
 3. Thesystem for stopping a spinning saw blade of claim 1, wherein the sensingassembly comprises a laser device.
 4. The system for stopping a spinningsaw blade of claim 1, wherein the sensing assembly comprises a sensorfor detecting the difference between the electrical capacitance of auser's hand and a workpiece.
 5. The system for stopping a spinning sawblade of claim 1, wherein the sensing assembly comprises a sensor fordetecting the difference between the electrical resistance of a user'shand and a workpiece.
 6. The system for stopping a spinning saw blade ofclaim 1, wherein the sensing assembly recognizes the differences betweenthe shapes of human body parts and a workpiece.
 7. The system forstopping a spinning saw blade of claim 1, wherein the pin assembly isactuated by a pyrotechnic device.
 8. The system for stopping a spinningsaw blade of claim 6, wherein the pyrotechnic device is included withina replaceable cartridge.
 9. The system for stopping a spinning saw bladeof claim 1, wherein the receiving block includes an aperture forreceiving the pin assembly.
 10. The system for stopping a spinning sawblade of claim 1, wherein the pin assembly is formed of hardened steel.11. A method of stopping a spinning saw blade, comprising: detecting auser's hand in a pre-defined zone by a detecting system; and driving apin assembly through the saw blade into a receiving block to stop thesaw blade from spinning upon detecting the presence of the user's hand.12. The method of claim 11, wherein the detecting system comprises avideo proximity device.
 13. The method of claim 11, wherein thedetecting system comprises a laser device.
 14. The method of claim 11,wherein the detecting system comprises a sensor for detecting thedifference between the electrical capacitance of a user's hand and aworkpiece.
 15. The method of claim 11, wherein the detecting systemcomprises a sensor for detecting the difference between the electricalresistance of a user's hand and a workpiece.
 16. The method of claim 1,wherein the detecting system recognizes the difference between theshapes of human body parts and a workpiece.
 17. The method of claim 11,wherein the pin assembly is actuated by a pyrotechnic device.
 18. Themethod of claim 17, wherein the pyrotechnic device is included within areplaceable cartridge.
 19. The method of claim 11, wherein the receivingblock includes an aperture for receiving the pin assembly.
 20. A saw,comprising: a pin assembly disposed adjacent to a saw blade assembly,the saw blade assembly being configured for receiving a saw blade, thepin assembly including a first end, the first end including a pointedtip for piercing the saw blade; a receiving block disposed on a side ofthe saw blade opposing the pin assembly for receiving the tip of the pinassembly; a driving assembly coupled to the pin assembly for driving thepin assembly into the saw blade and into the receiving block; and asensing assembly coupled to at least one of the saw blade assembly andthe driving assembly for sensing encroachment of a user's hand in apre-defined zone, wherein upon sensing a user's hand the sensingassembly signals the driving assembly to stop the saw blade by drivingthe tip of the pin assembly through the saw blade and into the receivingblock.